This invention relates to orthodontic equipment and, more particularly, to an improved orthodontic bracket for securing wires to teeth.
Brackets and wire are utilized in orthodontic procedures for the positioning of teeth. The brackets are secured to the teeth, and the wire is secured to the brackets. The brackets gripping the wire so as to transmit forces of wire twist and forces of wire bends as torques for rotating the teeth about various axis as well as for introducing linear translations to the respective positions of the teeth. The brackets may be secured to the teeth by conventional means, such as by adhesives or they may be secured to or form part of a band attached about a tooth.
With respect to the construction of the brackets, a multiple-sectioned bracket has advantages over a unitary one-piece monolithic bracket. For example, a multiple-sectioned bracket may be constructed of a base member which is secured to the tooth, and a block which is supported by the base and, in turn, is adapted for gripping a wire. Such a two-piece bracket is advantageous in that the wire supporting block may be replaced for a revised gripping of the wire without a disconnection of the bracket base from the tooth.
A problem arises in that while multiple sectioned brackets have been proposed, to date, no such bracket has proven successful in actual dental practice for a variety of reasons, including failure of adequate alignment between block and base, as well as difficulty in the disengagement of the block from the base. As a result, orthodontists and dentists have avoided the use of such multiple sectioned brackets due to the difficulty in obtaining the adequate accuracy of alignment, and due to the inconvenience experienced in the separation of block from base of the multiple-sectioned brackets.
The following U.S. patents are believed to be exemplary of the state-of-the-art of orthodontic brackets: U.S. Pat. No. 3,477,127; U.S. Pat. No. 3,660,900; U.S. Pat. No. 2,908,974; U.S. Pat. No. 4,186,488; U.S. Pat. No. 3,464,112; U.S. Pat. No. 3,464,113; U.S. Pat. No. 4,186,488; U.S. Pat. No. 4,244,898; U.S. Pat. No. 4,107,844; U.S. Pat. No. 3,964,165; U.S. Pat. No. 4,249,897; U.S. Pat. No. 3,930,311; U.S. Pat. No. 3,335,496; U.S. Pat. No. 3,946,488; U.S. Pat. No. 4,249,897; U.S. Pat. No. 3,881,252.
Of the foregoing patents, U.S. Pat. No. 2,908,974 of Stifter is of particular interest. Stifter discloses an anchor bracket of uniform size for each of a set of teeth and which is adapted to receive copy of a set of socket members having configurations for different wires. However, Stifter's bracket is to be entered from the side for insertion of a socket, this presenting an apparent difficulty when fixtures on neighboring teeth block such insertion.
Also of interest is U.S. Pat. No. 4,249,897 of Anderson which discloses inner and outer brackets, the inner bracket being deformable for the release of force associated with the wires interconnecting the brackets in a set of teeth.
The foregoing and other problems are overcome and other advantages are provided by an orthodontic bracket incorporating the invention, the bracket providing for precise alignment with the tooth and in the gripping of the wire as well as for facile engagement and disengagement from an outer or base element secured to the tooth. In accordance with the invention, the bracket comprises a wire gripping inner element block and a base to which the block is secured by spring tabs and alignment pins. As used herein, the term wire as understood includes any form of band, whether of metallic or non-metallic material.
Two spring tabs extend from the base, one tab being above the block and the other tab being below the block. The upper tab is provided with peripheral slots adjacent the base by which a U-shaped shim may be inserted between the base and the block for displacing the block from the base to release the tabs from the block. A pair of alignment pins extend from the rear of the block for insertion into correspondingly positioned alignment apertures within the base. The pins serve as a key and the apertures serve as a keyway for receipt of the key to provide for immediate alignment upon assembly of the base and block of the bracket. The foregoing arrangement facilitates manufacture of the bracket since the base can be fabricated of spring steel while any manufacturing tolerances are automatically compensated by the keying of the block to the base. The block being formed as a unitary monolithic structure, is readily manufactured by a molding operation, and may be suitably fabricated from a plastic material.